Test installation for single layer or multiple layer coating and drying of sheets of paper or film

ABSTRACT

The installation comprises at least one coater followed by an air jet-dryer. A sheet to be coated is joined at its ends to form an endless loop and moves continuously past the coaters and the drying zone. The variables of the drying air can be adjusted without any appreciable time-lag so that any drying programme can be simulated.

United States Patent Herzhoff et a1. Oct. 14, 1975 [54] TEST INSTALLATION FOR SINGLE LAYER 2,147,293 2/1939 Hansen 118/67 OR MULTIPLE LAYER COATING AND 3 323 323 3; 132 H322; DRYING 0F SHEETS OF PAPER 0R FILM 3:208:158 9/1965 Smith 34/122 [75] Inventors: Peter Herzhoff, Leverkusen; Hans 3,222,895 12/1965 sheppardmu 118/67 X G f C l H b t B k 3,284,920 11/1966 Hayriwen 34/122 1M 2 312 222 2/122; m "111154 Bensberg'Refrath of Germany 3:695:22O 10 1972 Garzotto 118/67 [73] Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen, Germany Prima Examiner-Rona1d Feldbaum [22] Flled: Sept 1973 Attorn y, Agent, or Firm-Connolly and Hutz [21] Appl. No.: 398,333

[30] Foreign Application Priority Data 57 A S C Sept. 23, 1972 Germany 2246798 The installation comprises at least one coater followed [52] US. Cl 118/68; 1 18/419 by an air jet-dryer, A sheet to be coated is joined at its 1111- (31-2 305C BO5C 3/12 ends to.form an endless loop and moves continuously Field of Search /58, 8, past the coaters and the drying zone. The variables of 155 the drying air can be adjusted without any appreciable time-lag so that any drying programme can be simu- [56] References Cited lated.

UNITED STATES PATENTS 1,772,081 8/1930 Hochstetter 118/67 X 8 Claims, 4 Drawing Figures U.S. Patent Oct.14,1975 Sheet10f4 3,911,863

FIG. 7

US. Patent Oct. 14, 1975 Sheet 2 of4 3,911,863

Sheet 3 of 4 US. Patent Oct. 14, 1975 Sh6t4 0f4 3,911,863

'l cmo 00 000000 8 BiBiolsioo m/min 10032100 ZHOOOO 75 300000 I 185003310 2 OBIBUEIO 4 $003810 a? ozszzzzo 0 2 0000 3 000181 OOO18i FIG. 4

TEST INSTALLATION FOR SINGLE LAYER OR MULTIPLE LAYER COATING AND DRYING OF SHEETS OF PAPER OR FILM This invention relates to a test installation for singlelayer or multiple-layer coating of sheets of paper or film with viscous solutions, followed by drying with air. An installation of this kind comprises at least one coater unit followed by an air jet dryer.

In the construction of production plants, for example for coating films or sheets or for drying materials, it is of considerable importance to know the coating and drying conditions under which the optimum product quality can be expected to be obtained before planning an installation.

It is also of considerable value when a product developed on a laboratory scale can also be tested on a small scale for its behaviour under the kind of conditions it is likely to meet in production so that it can be adapted to suit these conditions. Exact knowledge of these characteristics is the more important, the more the quality of a product or substance is influenced by manufacturing conditions, for example by the temperatures prevailing during drying, by moisture and air throughput. This is particularly the case with photographic products.

DAS l.962,089 relates to a multilayer coating installation in which the throughput of air required for drying can be varied within wide limits. This installation is intended for production and its size would make it uneconomical to use it for test purposes only. Although it would be conceivable to make an installation of this kind correspondingly smaller, there is a limit to the extent to which its size can be reduced because a certain minimum length is required for the drying sections. As a result, the installations are inevitably relatively large and expensive.

An object of the invention is to construct a simple, compact test installation for coating and drying sheets of film. The test installation according to the invention is intended to be able to simulate both the coating conditions and also the drying conditions as far as possible to correspond to production requirements.

According to the invention there is provided a test installation for single-layer or multilayer coating of sheets of paper or film with viscous liquids, followed by drying with air, comprising means for guiding the sheet in the form of an endless loop along a path, a coater for coating the sheet with a viscous liquid and an air-jet dryer downstream thereof for drying the coated sheet arranged along the said path, and a means for preparing the air fed to the air jet-dryer in which the variables of the drying air are adjustable without any appreciable time-lag.

In order to be able to establish different coating conditions, a plurality of coater units are advantageously arranged on a turntable or elongated platform beneath a sheet guide roller in the form of a coating roller. These coater units can be selectively moved up to the coating roller when the installation is in operation. The coater units can either be swung away or removed by means of linear guides.

In order to position the coater units accurately in relation to the coating roller, stops are advantageously provided. In this case, the coater units are preferably mounted on resilient elements so that their positions relative to the coating roller is determined solely by the stops.

Preferably the coater units are equipped with volume dispensers in the form of injection sprays. In this way, the coating solution can be dispensed independently of its viscosity and other flow properties.

The installation in which the drying air is prepared preferably comprises a fan, an air dessicator, a cooler, a heating system, a steam-injection chamber, a mixing chamber and of a pair of air flaps, all the components being connected in series. Basically, therefore, a constant throughput of air is used. In this installation for preparing the air used for drying, the drying air is adjusted to a constant initial condition. The air is then heated, moistened and quantitatively adjusted in accordance with the required condition of the drying air before it is fed to the air jet dryer. Accordingly, it is possible in this way to vary the drying conditions without any appreciable time-lag. For the same reason, the heating system should have a low heat capacity. Accordingly, the heating system is advantageously an electrical heating-wire system of low heat capacity which is arranged in the air stream and whose heat out put can be varied through varying the input of electrical power.

Another possibility of varying the variables of the drying air is to provide two air preparation installations which open into a common mixing chamber where that the two air streams differing in temperature and moisture content are mixed together in a selectable ratio. The mixing conditions can be gathered from Molliers I-X-diagram. They are limited by the line connecting the two initial air conditions in the l-X-diagram.

The primary advantages of the invention are the low space requirement and high flexibility of the installation. Only one dryer is required. The installation enables the important physical parameters for coating and drying to be optimised for production without excessive outlay.

One embodiment of the invention is described by way of example in the following with reference to the accompanying drawings, wherein:

FIG. 1 diagrammatically illustrates the structure of the test installation.

FIG. 2 illustrates the positioning of the coater units relative to the coating roller.

FIG. 3 illustrates preparation of the drying air.

FIG. 4 is a programme chart for one example of a coating and drying process.

As shown in FIG. 1, the sheet 1 bonded at its ends to form a continuous loop travels over a drum 2, guide rollers 3 and 4, a guide coating roller 5 and a flanged roller 6. At its ends, the flanged roller 6 has flanges over which the uncoated edge of the sheet 1 is guided. Contact with the freshly applied layer is avoided in this way. Beneath the coating roller 5 there is a turntable 7 on which coater units 8 are mounted. A coating solution is dispensed by means of injection sprays 9 which are driven through a spindle gear 10. Accordingly, the layer thickness applied is governed both by the amount of coating solution dispensed and by the rate of sheet travel.

Many types of coater unit have to be accurately positioned in relation to the coating roller. For this reason, stops 11 designed to come into contact with stop rings 12, are provided at both ends of the coater unit 8. The stop rings 12 are arranged at both ends of the coating roller 5. These four stops determine the critical interval between the coater unit 8 and the coating roller 5. In order to avoid mechanical stressing during positioning, the coater unit 8 is mounted on rubber blocks 13 (cf. FIG. 2). Instead of rubber blocks, it would of course alternatively be possible to use elastomeric materials. In the absence of this resilient mounting, the turntable and the stops would have to be made with extremely close tolerances because otherwise satisfactory contact would be impossible.

The coater unit 8 is horizontally positioned by means of the turntable 7. The coater unit 8 is raised by a penumatic unit 14 until its stops 11 come into contact with the stop ring 12. The movement is initiated under programme control. The individual working stages can of course alternatively be carried out by hand.

Coater units of the kind which function either on the wetting principle or on the extrusion principle are used for coating. Suitable types of coater unit are described for example in US. Pat. No. 3,635,192 and in US. Pat. No. 3,726,628.

After coating, the sheet travels into an annular air-jet dryer 15 where drying air is blown onto the sheet through the nozzles 16. Additional infra-red heaters 17 can be installed between the nozzles. The installation for preparing the drying air is shown in FIG. 3. The parameters which govern drying, namely the temperature, moisture and throughput of drying air, can be adjusted within wide limits without any appreciable timelag by means of this installation. These parameters determine the sheet temperature/time curve (drying characteristic) during the drying process. It has been found that, in the case of photographic materials, the quality of the end product is governed by the drying characteristic. The preparation installation described here enables the optimum drying characteristic to be determined.

Air is drawn in through a primary filter 19 by a fan 18 and is initially cooled in a cooler 20 and dehumidified in an air dessicator 21. The drying air then passes through another cooler 22 and a filter 23. Thereafter it is reheated by an electrical heating system 24 which consists simply of electrically heated wires. The intensity of heating is adjusted by adjusting the electrical power and regulated to a constant level. The heated air is then guided into a steam-injection chamber 25 and thoroughly mixed in the mixing chamber 26. Since all the components 19 to 26 of the preparation installation are connected in series, the throughput of air is always constant. The moisture content and temperatures of the drying air can be varied substantially without inertia by altering the output of the electrical heating system 24 and the steam-injection chamber 25. The quantity of drying air entering the air jet dryer 15 is adjusted by means of a pair of flaps 27. That part of the drying air which is not required escapes through a pipe 28. The quantitative ratio of the two air streams determines the rate at which the air issues from the nozzles 16. Accordingly, the air preparing installation always functions with a constant quantity of air.

It might have been thought appropriate to vary the quantity of air flowing into the dryer through the output of the fan. However, since the components between the fan 18 and the filter 23 have a relatively high heat capacity, this would have resulted in long adjustment times. In that case, the installation would only have reacted sluggishly to any changes. Since, in addition, the

quantity of steam sprayed into the stem-injection chamber 25 is always based on a constant quantity of drying air, the moisture content of the drying air reaching the dryer can readily be determined. The steam in- 5 jector can additionally be regulated through a moisture sensor and a control circuit. It is possible with this airpreparation installation to obtain any desired air condition between and 70C with air moisture levels of from x =1 g per kg to x =16 g per kg. The changes in moisture are sudden whilst the changes in temperature take place within a matter of seconds.

By virtue the use of the turntable arrangements with various types of coater unit and the capability of the installation used to prepare the drying air for a wide range of variation, it is possible to simulate a wide range of coating and drying conditions. In many cases, drying has to be carried out in accordance with a certain drying characteristic. In that case, it is best continuously to record the temperature of the coated sheet as it passes through the dryer, the temperature of the drying air and its moisture content. It is possible by means of a control circuit (not shown) to control the variables of the drying air in such a way that the temperature of the sheet has the required value at any time during the drying process.

The mode of operation of the installation is explained below with reference to the programme chart shown in FIG. 4 which relates by way of example to two-layer coating. The sheet 1 travelling at a speed of 25 meters per minute is coated with a layer having a thickness of 40 g/m by a coater unit of type A (wetting coater) over a distance of about meters. The coated sheet then enters the dryer 15 where it is dried under three different drying conditions. In this case, the continuous path length of the sheet is about 5 meters and its width approximately 16 cm. The diameter of the drum 2 in the dryer is about 130 cm.

As indicated by crosses in the programme chart, the sheet 1 is initially dried for 30 seconds at 25C( 16 8 1C) with air containing 5 g of moisture per kg of air issuing from the nozzles 16 at a rate of meters per second. The sheet 1 then passes for seconds through a zone where it is dried at 40C with air having a xvalue (moisture content) of 10 g per kg and a rate of flow of meters per second. Finally, it enters a third zone where it is dried for 20 seconds at 20C with air having a-x-value (moisture content) of 10 g per kg and a rate of flow of 5 meters per second.

The second layer is then applied to the sheet travelling at a rate of meters per minute by a type C coater which is an extruder coater. The second layer is then dried for seconds at 30C with air having a x-value (moisture content) of 7 g per kg and a rate of flow of 20 meters per second. This last drying operation alone would require a drying section approximately 53 meters long in a conventional continuous machine. In the installation described above, purely by way of example, the maximum rate of travel of the sheet is 50 meters per minute and the maximum processing time minutes (10 X 16 minutes). If these same limit values were to be used as the basis for a conventional continuous machine, it would have to have a length of 50 X 160 8,000 meters which is intolerable under any circumstances. 7

An alternative installation uses two air-preparing installations of the kind shown in FIG. 5 differing from one another in their dimensions. The two air streams of air which differ in temperature and-moisture content are mixed together in a mixing chamber. Any desired point on the straight line connecting the condition points in Molliers i-x-diagram can be reached without any appreciable time lag by rapidly changing the mixing ratios.

What we claim is:

1. A test installation for single-layer or multilayer coating of sheets of paper or film with viscous liquids, following by drying with air, comprising means for guiding the sheet in the form of an endless loop along a path, a coater for coating the sheet with a viscous liquid operatively arranged at a station upon the endless loop, an air-jet dryer downstream thereof for drying the coated sheet arranged along the path, a means for pre paring the air fed to the air-jet dryer in which the variables of the drying air are adjustable without any appreciable time-lag whereby drying conditions along a long path which is a multiple of the length of the endless loop are simulated, the coater including a guide coating roller about which a portion of the endless loop of sheet is disposed in a protruding portion of the endless loop, the coater also including a base disposed externally of the endless loop, coating liquid supply means connected to the base of the coater, a movable platform mounted externally of the endless loop adjacent the protruding portion disposed about the coating guide roller, a plurality of coater bases mounted on the movable platform for selective engagement with the protruding portion of the endless loop, transverse moving means connected to the platform for selectively positioning one of the bases in alignment with the protrud ing portion of the endless loop disposed aboutthe guide coating roller, and longitudinal translating means connected to the platform for moving it and the coater bases disposed upon it toward and away from the protruding portion of the endless loop whereby one of the coater bases is operatively engageable with the protruding portion of the endless loop to apply liquid to it and is movable away from it.

2. An installation as claimed in claim 1 wherein mutually engaging stops are provided on the coating guide roller and coater bases for accurately positioning the coaters relative to the coating guide roller when they are operatively engaged with each other.

3. An installation as claimed in claim 2, wherein the coater bases are mounted on resilient elements so that their position relative to the coating roller is determined solely by the stops.

4. An installation as claimed in claim 1 the or, wherein the or each coater base comprises a volume dispenser in the form of injection sprays.

5. An installation as claimed in Claim 1 wherein the air preparing means comprises a fan, an air dessicator, a cooler, a heating system, a steam-injection chamber, a mixing chamber and a pair of air flaps all of which are connected in series.

6. An installation as claimed in claim 5, wherein the heating system is an electrical heating-wire system of low heat capacity which is arranged in the air stream and whose heat output can be adjusted through adjusting the electrical power.

7. An installation as claimed in claim 1, wherein the air preparing means comprises two air-preparation installations which open into a common mixing chamber where the two air streams differing in temperature and moisture are mixed together in a selectable ratio.

8. An installation as claimed in claim 1 wherein the movable platform comprises a turntable and the coater bases are radially mounted upon the turntable. 

1. A test installation for single-layer or multilayer coating of sheets of paper or film with viscous liquids, following by drying with air, comprising means for guiding the sheet in the form of an endless loop along a path, a coater for coating the sheet with a viscous liquid operatively arranged at a station upon the endless loop, an air-jet dryer downstream thEreof for drying the coated sheet arranged along the path, a means for preparing the air fed to the air-jet dryer in which the variables of the drying air are adjustable without any appreciable time-lag whereby drying conditions along a long path which is a multiple of the length of the endless loop are simulated, the coater including a guide coating roller about which a portion of the endless loop of sheet is disposed in a protruding portion of the endless loop, the coater also including a base disposed externally of the endless loop, coating liquid supply means connected to the base of the coater, a movable platform mounted externally of the endless loop adjacent the protruding portion disposed about the coating guide roller, a plurality of coater bases mounted on the movable platform for selective engagement with the protruding portion of the endless loop, transverse moving means connected to the platform for selectively positioning one of the bases in alignment with the protruding portion of the endless loop disposed about the guide coating roller, and longitudinal translating means connected to the platform for moving it and the coater bases disposed upon it toward and away from the protruding portion of the endless loop whereby one of the coater bases is operatively engageable with the protruding portion of the endless loop to apply liquid to it and is movable away from it.
 2. An installation as claimed in claim 1 wherein mutually engaging stops are provided on the coating guide roller and coater bases for accurately positioning the coaters relative to the coating guide roller when they are operatively engaged with each other.
 3. An installation as claimed in claim 2, wherein the coater bases are mounted on resilient elements so that their position relative to the coating roller is determined solely by the stops.
 4. An installation as claimed in claim 1 the or, wherein the or each coater base comprises a volume dispenser in the form of injection sprays.
 5. An installation as claimed in Claim 1 wherein the air preparing means comprises a fan, an air dessicator, a cooler, a heating system, a steam-injection chamber, a mixing chamber and a pair of air flaps all of which are connected in series.
 6. An installation as claimed in claim 5, wherein the heating system is an electrical heating-wire system of low heat capacity which is arranged in the air stream and whose heat output can be adjusted through adjusting the electrical power.
 7. An installation as claimed in claim 1, wherein the air preparing means comprises two air-preparation installations which open into a common mixing chamber where the two air streams differing in temperature and moisture are mixed together in a selectable ratio.
 8. An installation as claimed in claim 1 wherein the movable platform comprises a turntable and the coater bases are radially mounted upon the turntable. 